Rio Ferdinand fears Manchester United might have repeated the mistake they made in allowing Jaap Stam to leave by letting Nemanja Vidic join Inter Milan.

Ferdinand's centre-half partner, 32, will join the Italians on a free transfer this summer, 13 years after Sir Alex Ferguson made a call he later regretted in offloading Stam to Lazio.

Former United manager David Moyes has previously described Vidic's move as 'the right decision for club and player', but Ferdinand said: 'Only time will tell if Manchester United regret allowing him to leave.

'Obviously
Jaap Stam played on for quite a few years at a good level after he left
Man United and the same thing could happen with Nemanja. He's a great
player and it's a shame he had to leave.'

Ferdinand,
speaking at the launch of the BBC's World Cup coverage, also believes a
fully-fit Wayne Rooney can excel in Brazil this summer after his
struggles at every major championship since he impressed at Euro 2004.

But he stressed the importance of Roy Hodgson and the future United manager not attempting to tame the volatile striker.

Ferdinand
said: 'He has always limped into a tournament, he has always had
problems injury wise.

'If you get a fresh Wayne Rooney going into a
tournament, like we saw in Euro 2004, when he was young and fresh with
no injuries, you saw a guy who frightened teams to death.

Milan-bound: Vidic will join Inter on a free transfer this summer at the age of 32

'I
think he still has the capability to do that. You see that in a
Manchester United shirt often enough. If he goes into a tournament fit,
it gives England a better chance of doing well because he scores goals.
Simple as that.'

When
asked about Rooney's temperament, Ferdinand said: 'He is a big lad now.
He is older, more mature. He has been in a lot of situations - he has
been in every situation a player can be in.

'I
have no worries about him dealing with that. I would rather see Wayne
Rooney sent off once or twice a season because I want him to keep that
fire in his belly.

'I don't want people to take that spark out of
players, because I think you lose something out of their game.'

Bad call: Manchester United were left to regret letting Jaap Stam (right) leave in 2001

Ferdinand,
meanwhile, believes England's opening Group D fixture against Italy
will be crucial in determining if they survive the first round. He said:
'I think it is important that we get out of the first game with points
on the board. If we do that then I think it is a given that we will get
out of the group.

'The
first game against Italy is important. They will be more wary of us and
if you look at it on paper, I think they have got to be more wary of us
with the players we have got in the attacking part of the pitch.

This is his time: Ferdinand believes United team-mate Wayne Rooney can excel in an England shirt in Brazil

'They
will have to be worried about that with the pace and the youth and the
exuberance and the enthusiasm we are going to have in the first game.
Hopefully that gets us flying out of the traps like greyhounds.

'Uruguay
have an unbelievable strength in their attack, with the two guys up
front, but their weak point is their defence, so I think we have a good
chance. Costa Rica is the unknown package.'

Top team: Ferdinand (second left) is part of the BBC's World Cup television coverage this summer